Oxidation of secondary alcohols



Patented Aug. 1, 1944 OXIDATION OF SECONDARY ALCOHOLS David 0. Hull,Klngsport, Tenn, assignor to Eastman Kodak Company, Rochester, N. Y., acorporation of New Jersey No Drawing. "Application May 1, 1942, SerialNo. 441,269

3 Claims.

This invention relates to the direct oxidation of organic compounds,particularly hydroxy com- 1 pounds exemplified by secondary alcohols.This invention is particularly adapted to the direct oxidation of suchsecondary alcohols to ketones and esters, and will be describedhereinafter.

This invention isa continuation-in-part of my allowed application SerialNo. 228,822, filed September 7, 1938, now Patent No. 2,287,803.

As set forth in my parent application aforesaid, prior to my inventionin the prior art in order to convert hydroxy compounds to other productsit has been necessary to employ relatively high temperatures such astemperatures between 200 C. and 500 C. In more detail, for example, inthe instance of converting a secondary alcohol into a ketone, inaccordance with the prior art procedure the secondary alcohol in thevapor phase wouldbe contacted with a solid catalyst at relatively hightemperatures of several hundred degrees centigrade. Proceeding inaccordance with prior art practice possesses certain dislosses andinvolves the handling of combustiblematerial'in which the flreiiazard isexceptionally high due to the elevated temperatures involved.

In my Patent No. 2,287,803 I have described treatment: particularlyadapted for conversion primary alcohols whichovercomes the aforesaiddisadvantages, and in the present application I describe a directoxidation procedure particularly adapted for the treatment of secondaryalcohols which represents a substantial improvement over prior artprocedure employed for the treatment of such compounds.

This invention has for one object to provide a direct oxidation processparticularly adapted to the treatment of organic compounds having abydroxy group in the secondary position, as for example on anintermediate carbon atom, as the a 01' 4 position, etc. Another objectis to provide a process permitting the direct conversion by oxidation ofsecondary alcohols to ketones. A still further object is to provide anoxidation process which may be operated at relatively low temperatures.Still another object is'to provide a process for oxidizing organiccompounds which, after it has been started, is more or less selfmaintaining as respects heat input. Still another object is to provide anovel catalyst solution for carrying out the aforesaid processes. Otherobjects will appear hereinafter.

I- have found that the aforesaid secondary hydroxy compounds may bedirectly oxidized at a relatively low temperature under liquid phaseconditions to ketones and other oxidation products. Examples of some ofthese secondary compounds. are compounds such as isopropyl and secondarybutyl alcohols from which may be obtained by my direct oxidation processketones and acids and, also, some esters. Also there may "be treated ina similar manner various secondary amyl alcohols, secondary hezqzlalcohols, secondary heptyl alcohols, and secondary octyl alcohols. Underpreferred conditions, as I will point out in detail hereinafter, I woulddirectly oxidize such secondary compounds in the presence of an acidiccatalystsolution containing as a catalyst a metal compound from a metalof the 8th group of the periodic system. However, as willv be pointedout, various other metal compounds will satisfactorily function, hence,the broader aspects of my invention embrace other catalysts. In anyevent, irrespective of the particular catalyst metal employed. thecatalyst solution may contain a certain amount. of the alcohol beingprocessed and the catalyst solution would preferably be in an activatedcondition both before and durini;

The catalyst solution would have present a content of water which ispreferably small and, also,

in some instances a small content of an alcohol of the type'undergoingprocessing.

In preparing the catalyst solution various compounds of the catalystmetal may be incorporated into the acid solution as long as a compoundis employed which goes into solution satisfactorily. That is,considering cobalt as an example of the catalyst metal, there could beemployed cobalt oxides, cobalt acetate, or other ester salts or othercompounds, such as strontium acetate, aluminum acetate, silver acetate,chromium acetate and uranium acetate. V After the catalyst materials areincorporated in the acid or other solvent, as for example a mixture ofacid and alcohol, the solution would be vigorously treated with air,oxygen, or other oxidizing medium, preferably under some pressure, and acontent of a carbonyl compound also supplied alon with the airintroduction. For example, the introduction of a content of a loweraliphatic aldehyde such as butyraldehyde and the like aids in theactivation. Various other aldehydes could be employed such aspropionaldehyde and acetaldehyde.

The aforesaid activation treatment would be carried out at a temperaturebelow the boiling point of the particular catalyst solution andgenerallytemperatures under 100 C. are quite satisfactory, usually untila substantial content of the catalyst metal has become converted to avalence higher thanits lowest valence, or until the gaseous mediumcontaining free oxygen (such .as air) being introduced has so permeatedthe entire solution that the solution is on the verge of efiervescence.

The preferred catalyst metal would be the same as described in my PatentNo. 2,287,803, namely/ cobalt and related metals. As described in saidparent application, a content of cobalt acetate could be dissolved inacetic acid and the resultant solution activated, as already described.

While cobalt and the metals referred 'to in my copending parentapplication are preferred, other catalyst metals may be employed in thetreatment of secondary alcohols. Secondary alcohols'appear to be lessdifllcult to oxidize than the other alcohols described in my Patent No.2,287,803.

described in Mellors Chemistry at page 641, or.

metals of the refractory type such as chromium, molybdenum, tungsten,and the like operate satisfactorily. v

In general I have found that in the oxidation of secondary alcohols thecatalyst solution may comprise an acidic solution preferably of a lowerorganic acid having dissolved therein a metallic compound, whichsolution is capable of activation with an aldehyde, as above described.

The catalyst solution, whatever its particular composition, but which inaccordance with my preferred embodiment would include a cobalt compound,would be placed in .the oxidation apparatus and preferably activatedtherein by the treatment with the oxidizing medium and aldehyde, asalready described.

Oxidation apparatus the same as that described in my Patent No.2,287,803 may be employed for the treatment of secondary alcohols, inaccordance with the present invention, or apparatus such as shown inHasche U. El.- Patent No. 2,159,988 may be employed. In general theapparatus should comprise suitable means for bringing the secondaryalcohol to be oxidized in contact with a liquid catalyst solution alsoin contact with the oxidizing medium containing free oxygen. Suitableprovisions would be made for controlling the temperature, preferably byhaving a plurality of coils positioned within the reaction chamber sothat the coils are immersed in the catalyst solution. However, thejacketed oxidation units or a combination of jacketed units withinternal coils may be employed.

Also preferably there would be suitable means for dispersing theoxidizing medium and other components fed to the unit; however, sinceprovision for this is fully described in Hasche Patent 2,159,988,further description herein is unnecessary.

Assuming, therefore, that suitable oxidation apparatus is supplied witha catalyst liquid capable of activation and which has been activated byoxygen and aldehyde, secondary alcohols may be oxidized as follows: Thealcohol, together with preferably a slight excess of the oxidizingmedium, would be blown into the unit so as to bubble through thecatalyst solution in intimate contact with the oxidizing medium. Alsofrom time to time, or if desired in a small continuous stream, a certainamount of lower aliphatic aldehyde may be supplied to the process forassisting in maintaining the catalyst activity.

I have found that. irrespective of the particular metal compoundemployed with the aforesaid activation, oxidizing the medium andaldehyde, either before carrying out theoxidation step of the process orin=conjunction therewith, greatly improves the oxidation, extends thelife of the catalyst solution and renders possible the utilization of avery large variety of metal compounds as catalysts.

The oxidation procedure, in accordance with my invention, concerns theconversion of secondary alcohol to ketone and ester. Also, certain otherproducts are formed, as will be described in further detail under thespecific examples which follow.

The products which are formed may be removed from the process bywithdrawing a portion of the catalyst solution from the upper part ofthe unit or some other convenient point and sublecting it todistillation or other treatment for separating the reaction products,after which the catalyst solution may be returned to the process. or bytemperature regulation so that there is a constant volume of catalystsolution with a quantity equal to the weight of the products formed,boiling off continuously.

For example, assuming th secondary alcohol treated was lsopropanol, theresulting catalyst solution, after the oxidation, would contain acetoneor certain other reaction products. The solution may be substantiallycontinuously removed from the oxidation, subjected to distillation forvolatilizing off the acetone, and the resulting stripped catalystsolution returned to the process.

For a still further understanding of my invenc eeses ferredcatalyst.namely, a catalyst solution con-' 5 taining an activated cobaltcompound.

. Example VI In accordance'with this example secondary hexyl alcohol ofthe formula cm-cni-cni -cnon-cni-cm was processed in the presence of acatalyst solu- Materials Per cent converted tox 'lotal .lotai ExamplesCompound Catalyst I no Weight Weight Weight 9 ketcne ester acid W Add VJ I Ilopmpyl hol. Cobalt m7 936 125.3' 88 782 7.53 ldfi 18.2 91.2 H'...do dn 827.0 400 114.6 130.3; 604 9.25 14.30 9.45 96.0 In B00. butyl001101 b!" nickel 705 l. m 349. 0 32 91 2. 81 50.8 3 8. 16 70. 9

lncludmd. lonicaoidand81g.aoctic a lncludemwo nv.

aci to propionic acid and 7.61% conv. to acetic acid. I t

The foregoing examples were carried out at temperatures betweenapproximately 30 C. and 60 C. obtained by the supplying of coolingmedium to coils positioned within the reaction chamber. The process wasoperated so that the catalyst solution was maintained in the liquidphase and at constant volume, the temperature being so regulated thatthe same amount of liquid distilis of! as is added and after the processhas been placed in operation, it generates sufllcient heat to beself-maintaining, particularly if the catalyst is kept in an activecondition.

1.1 the examples which follow the procedure was similar to thatindicated in the foregoing examples except that wider temperature rangeswere employed, asbetween C. and 90 C. By applying pressure highertemperatures up to 140 C. or higher may be employed and still operateunder liquid phase conditions. However, in general not over a few poundspositive pressure is preferred and utilization of low temperatures isadvantageads for preventing polymerization as well as avoiding thenecessity of any substantial heat input, as discussed in the first partof the present application.

Example IV In accordance with this example secondary amyl alcohol of theformula CHa-CHr-CHs-CHOH-CH:

slight excess of air as an oxidizing medium. This secondary alcohol wasconverted approximately between 1% to 10% to secondary amyl ester,

to 70% to methyl propyl ketone, 2% to 20% propionic acid, and 1% to 15%acetic acid. There are also varying traces of other acids, probablyformic and butyric acids. The process was operated with sumcient coolingmedium supplied to the coils to maintain the catalyst in a liquidcondition.

Example V In accordance with this example a amyl alcohol of the formulav secondary tion containing a mixture of cobalt and nickel,

the catalyst having been thoroughly activated prior to the contacting ofthe secondary hexyl alcohol therewith. Substantially simultaneous withthe introduction of the secondary hexyl alcohol theme was alsointroduced air as the oxidizing medium and intermittently acetaldehydewas supplied. The hexyl alcohol was converted-approximately up to 10% tothe secondary hexyl ester, 20% to to ethyl propyl ketone, and a contentof propionic, acetic, and butyric acid formed. It appears that thepropionic acid predominated, amounting to between 2% and 30%.

Example VII In accordance with this example seconda hexyl alcohol of theformula K was processed substantially similar to that described inthepreceding example. There was obtained secondary hexyl ester up to10%, 10% to 10% methyl butyl ketone, and varying amounts of acids asbetween 1% to 15% or 20%. acetic and butyric acid. These acids may alsohave in admixture therewith small amounts of formic and valeric acid.

' The preferred operating temperatures of the foregoing examples wouldpreferably be under C. if normal atmosphere. pressure or only a slightpositive pressure were applied. However, the reaction may be caused toproceed'even at temperatures as low as a 5 C. and at temperatures above100 0., particularly the higher temperatures when pressure is applied tothe reaction as by throttling the outlet conduit at the top of theoxidation unit.

. The highest yields appeared to be obtainable when my preferred cobaltor cobalt nickel catalyst was employed, namely, a catalyst as describedin my Patent No. 2,287,803. However, satisfactory results may beobtained when utilizing alkali or alkaline earth metal compounds as thecatalyst material. As long as the catalyst was in an activated conditionthis appeared to exert as muchinfluence on the satisfactoriness of theoxidation as the choice of any specific catalyst metal or mixture ofmetals.

The unconsumed secondary alcohol leaving the oxidation unit may berecovered by distillation or in some other way.

While air was used as the oxidant in the preceding examples, relativelypure oxygen and ozone may likewise be employed. However, air being themost economical and since my oxida:

particularly if a catalyst liquid is in a fully acti-:

vated condition, the employment of more concentrated or vigorousoxidizing mediums is optional.

with respect to proportions in my preferred operation, as aboveindicated I would supply sufflcient oxidizing medium to the process sothat some unused oxidant, but usually less than'50% excess, would appearin the eilluent' gases from the process. As to the incorporation ofaldehyde such as acetaldehyde, propionic aldehyde, butyraldehyde, orother aldehydes for catalyst activaof the lower aliphatic acids as thesolvent me-- dium in which to dissolve the metal compound for preparingthe catalyst solution.

With respect to quantity of alcohol employed, this does not appear to becritical and various quantities appear to function satisfactorily in myprocess. In practice,.however, I would generally apply my process to thetreatment of commercial sources of alcohol. For example, in the instanceof isopropyl alcohol the so-called commercial azeotropic mixture,namely, a mixture of isopropyl alcohol and water, would be processed andeven considerably more dilute solutions may be treated, but due to theirtendency to dilute the catalyst would not be preferred. That is, in myprocess a very dilute alcohol, such as dilute isopropyl alcohol, may beeasily concen'trated to the azeotrope by conventional procedure and theazeotrope fed to the process. Similar remarks apply to the othersecondary alcohols, some of which form constant boiling mixtures withwater. The alcohol, either in a dilute or concentrated condition as maybe desired, may have in admixture therewith, or there may be suppliedsimultaneously or intermittently with the alcohol supply, a content of alower aliphatic aldehyde, as already disclosed. In general at least 4%or 5% of the aldehyde would be preferred, and amounts up to 50% or 75%may be employed. The higher the amount of the aldehyde the higher thecontent of acid in the i temperatures, namely, temperatures such asthose at which the secondary alcohols may be maintained under liquidphase conditions; The utilization of liquid phase conditions andrelatively low temperatures not only involves less heat input, but theless severe conditions present fewer difliculties from apparatusdestruction, fire hazard, and losses by heat polymerization. It is alsobelieved apparent from the foregoing that my invention is applicable tothe oxidation of a number of secondary alcohols of which the foregoingexamples are merely illustrative.

What I claim and desire to besecured by Letters Patent of the UnitedStates is:

l. A process for the direct oxidation of a lower aliphatic secondaryalcohol to obtain the corresponding ketone which comprises treating asolu- 1 tion of a metal ion of a metal numbered 25-29,

inclusive, of the periodic table in an-aliphatic acid with an aldehydeand a gaseous oxidizing medium to form a catalyst solution, introducingmaterial amounts of a lower aliphatic secondary the liquid-phase, andsubsequently recovering the ketone produced.

2. A process for the direct oxidation of a lower aliphatic secondaryalcohol to obtain the corresponding ketone which comprises treating asolution of a metal ion of a metal numbered 25-29, inclusive, of theperiodic table in an aliphatic acid with an aldehyde and a gaseousoxidizing medium to form a catalyst solution, introducing materialamounts of a lower aliphatic secondary alcohol and a lower aliphaticaldehyde into the activated catalyst solution, oxidizing the alcohol ofthe resulting solution of catalyst, alcohol and aldehyde by treatingsaid solution with a gaseous oxidizing medium, maintaining thetemperature v of the solution of catalyst, alcohol and aldehyde isdesired to-build up the acid content, this can,

from 5 to C. during its treatment with the gaseous oxidizing medium,whereby the solution is maintained in the liquid phase, and subsequentlyrecovering the ketone produced.

3..A process for the direct oxidation of a lower aliphatic secondaryalcohol to obtain the corresponding ketone which comprises treating asolution of a cobalt salt in an aliphatic acid with an aldehyde andagaseous oxidizing medium to form a catalyst solution, introducingmaterial amounts of a lower aliphatic secondary alcohol and a loweraliphatic aldehyde into the activated catalyst solution, oxidizing thealcohol of the resulting solution of catalyst, alcohol and aldehyde bytreating said solution with a gaseous oxidizin medium, maintainingthetemperature of the solution of catalyst, alcohol and aldehyde during itstreatment with the gaseous oxidizing medium at a temperature below 100C. whereby the solution is maintained in the liquid phase, andsubsequently recovering the ketone produced.

. DAVID c. HULL.

